Electrical coupling structure



ly 1953 G. E. HULSTEDE 2,646,511

ELECTRICAL COUPLING STRUCTURE Filed March 4, 1946 fl 4 l3 i I474 j 5 b i2 2 25a I Z in V 4 I INVENTOR GEORGE E. HULSTEDE ATTORNEY Patented July 21, 1953 ELECTRICAL COUPLING STRUCTURE George E. Hulstede, Belmont, Calif., assignor to the United States of America as represented by the Secretary of War Application March 4, 1946, Serial No. 651,940

. Claims. 1

This invention relates generally to electrical apparatus and more particularly to a multiple feedback device for use in the feedback portion of a resonant coaxial line oscillator.

In one type of radio frequency oscillator, two resonant coaxial lines are connected between the grid and plate and the grid and cathode, respectively, of a triode vacuum tube to form the resonant circuits of the oscillator. The lengths of the resonant coaxial lines may be varied in order to, allow the frequency of oscillation to be adjusted. Feedback probes are provided between the gridplate and the grid-cathode coaxial resonant lines.- The feedback probes which have been employed heretofore, enabled the oscillator to operate satisfactorily over only a limited frequency range. Accordingly, one object of this invention is to provide a feedback means which affords adequate coupling between two coaxial resonant lines for frequencies over a relatively wide range.

Another object is to adapt the aforesaid feedback means to any application wherein a relatively wide band of frequencies are to be coupled from one coaxial resonant line to another.' It follows that for any cavity or in other instances where wide-range feedback is desired, the feedback system for coaxial resonant lines as disclosed herein may prove applicable.

Other objects, features and advantages of this invention will suggest themselves to those skilled in the art and will be apparent when taken in connection with the accompanying drawings in which:

Fig. 1a is a top view of a feedback assembly embodying the principles of this invention;

Fig. 1b is a vertical sectional view of the aforesaid feedback assembly; and

Fig. 2 is a schematic diagram of a dual coaxial resonant line, radio frequency oscillator including the feedback assembly shown in Fig. 1.

In Fig. 1b a vertical cross-sectional view of two concentric coaxial lines are shown. Cylinder I0 is concentrically spaced about center conductor [9. Cylinder surrounds cylinder l0 and is also concentrically spaced with respect to center conductor IS. The cylinders Ill and 20 form a first resonant coaxial line 2|. Cylinder l0 and center conductor [9 form a second resonant coaxial line 22. Radio frequency energy over a relatively wide band of'frequencies is to be coupled from the first resonant coaxial line to the second. 7

One end of a loop of metal conductor I l is connected to the outer surface of cylinder Ill. The opposite end of the loop II projects through a hole 12 in cylinder I0, and, when bent and connected to the inner surface of the cylinder, forms a second loop I3 inside the cylinder. The combination including loops II and [3 will hereinafter be referred to as the inductive probe 14.

Diagonally opposite the inductive probe I4 2. capacitiveprobe I5 is attached to cylinder l0. Capacitive probe [5 includes a loop of metal conductor 16 within cylindrical ring l0, one end of" which is attached to the interior surface of cylinder H3 and the opposite end of which projects through hole I! in the cylinder. A circular disc [8 (side view shown) is attachedto the projecting end of the metal conductor 16 on the outside of the cylinder. Circular disc I8 is substantially the capacitive coupling portion of capacitive probe l5. The exact shape of the circular disc I8 may be altered to fit particular requirements.

A plurality of inductive and capacitive probes as l4 and I5 may beequally spaced around the circumference of the cylinder [0. This is more clearly shown in Fig. 1a, in which three inductive probes M are shown, symmetrically spaced about quency oscillator, of the type, for example, de-

scribed in a patent by Eugene Fubini, Hegar C. Kriegel, and John C. Stevenson, entitled High- Frequency Concentric Line Oscillator, Serial No. 651,310, filed March 1, 1946, Patent No. 2,472,204, issued on June 7, 1949. The radio frequency oscillator referred to above is shown in, the schematic diagram of Fig. 2.

The aforesaid radio frequency oscillator includes a triode vacuum tube 53 having a cathode 54, a control grid and a plate 56. A cylinder 50 is surrounded by a concentric hollow cylinder 5|. Hollow cylinder 5| is surrounded by a concentric hollow cylinder 52. Concentric cylinder 5| is connected directly to the control grid 55 of the triode 53. Cylinders 50 and 52 are capacitively coupled through capacitors 51 and 58,. re spectively, to cathode 54 and plate 56, respectively, of triode vacuum tube 53.

Cylinder 59 together with concentric cylinder 5| forms a resonant coaxial line between the control grid 55 and the cathode 54 of the triode vacuum tube 53. Concentric cylinder 5! together with concentric. cylinder 52 forms a resonant coaxial line between the control grid 55 and the plate 56 of the triode vacuum tube 53. The

Fig. 2 is provided by means of the feedback device shown in Fig. 1. The cylinders and 2B in Fig. la are represented in Fig. 2 as a continuation of the cylindrical conductors 5i and 52, respectively. Inductive probe 14 projects through hole 6| in cylindricalconductor 5i. Capacitive probe l5 projects through hole 62 in cylindrical conductor 5|. One inductive probe l4 and one capacitive probe l5 have been shown in Fig. 2 for purposes of illustration only. Any desirable symmetric arrangement including more than one of each probe may be used when found applicable.

A suitable positive potential from a source designated herein as Eb is applied to plate 55 of triode vacuum tub 53 through radio frequency choke 63. To discBd is applied a. suitable bias potential from a source designated herein as Eg. Disc 54, as mentioned beforehand, is connected to cylindrical conductor 5! which in turn is connected to control grid 55 of triode vacuum tube 53. To cathode 54 of triode vacuum tube 53 is applied a suitable potential from a source designated herein as Ea.

The oscillator circuit is tunable to a particular frequency by adjusting the respective terminating ends 59 and 60 of the grid-cathode and the I grid-plate coaxial resonant lines. For the oscillator to operate satisfactorily the feedback probes l4 and must return a voltage of the proper phase, frequency, and amplitude from the gridplate resonant line to the grid-cathode resonant line.

At frequencies of oscillation below a certain value the field configuration in the coaxial resonant lines becomes predominantly of a transverse magnetic mode. At these frequencies the inductive probes are more effective in feeding back a voltage of sufficient amplitude to sustain oscillations.

At frequencies of oscillations above said value the field configuration in the coaxial resonant lines becomes predominantly of a transverse electric mode. At these frequencies the inductive probe coupling becomes less effective and the capacitive prob coupling becomes more effective.

A greater range of feedback frequencies may be covered by the above-described feedback system than would be possible by using capacitive or inductive probes separately. The number and size of the inductive and capacitive coupling probes is governed by the total amount of feedback energy which is desired. The symmetrical spacing of the probes within the coaxial resonant lines allows the electrical fields to be symmetric and prevents undesirable modes of oscillation from becoming dominant.

It would be evident to those skilled in the art that such a feedback system entailing the principles of this invention can b used in coupling any type of resonant cavities or resonant coaxial lines together.

While there has been described hereinabove what is at present considered to be a preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from th scope of the invention as set forth in the appended claims.

What is claimed is:

1. In a coaxial line oscillator for generating radio frequency energy and including two coaxial resonant lines having a common metallic member, a plurality of inductive probes spaced symmetrically around the circumference of said metallic member and each extending through said metallic member to form a p on each side thereof, and a plurality of capacitive probes spaced symmetrically around the circumference of said metallic member and each extending through said metallic member to form a loop on one side thereof, each of said'capacitive probes being terminated by a metallic disc on the opposite side of said member, said probes serving to provide feedback between said lines.

2. In a coaxial line oscillator for generating radio frequency energy and including two coaxial resonant lines having a common member, a plurality of inductive probes spaced symmetrically around the circumference of said member and extending through said member, and a plurality of capacitive probes spaced symmetrically around the circumference of said member and extending through said member, said probes serving to provide feedback between said lines.

3. In combination with a plurality of coaxial resonant lines having at least one member in common, a plurality of inductive coupling means projecting through said common member, and a plurality of capacitive coupling means projecting through said common member, said inductive and capacitive coupling means serving to couple said plurality of resonant lines together.

a. In combination with a plurality of cavity resonators having at least one member in common, a plurality of inductive coupling means projecting through said common member, and a plurality of capacitive coupling means projecting through said common member, said inductive and capacitive coupling means serving to couple said plurality of cavity resonators together.

5. In an ultra-high frequency electrical apparatus including a'plurality of inclosures having at least one member in common, means for inductively coupling adjacent inclosures through said member, and means for simultaneously capacitively coupling said adjacent inclosures through said member.

GEORGE E. HULSTEDE.

References Cited in the file of this patent UNITED STATES PATENTS 

